成人髋臼发育不良髋臼内壁内移截骨的有限元分析

背景：成人髋臼发育不良晚期并发髋关节骨性关节炎常需行全髋关节置换。由于不同患者髋臼病变的严重程度有很大差别，导致重建髋臼时难度明显增加，而髋臼内壁内移截骨能良好解决对臼杯假体的包容，但对截骨后髋臼内壁的内移范围仍存有争议。 目的：通过计算机辅助设计有限元分析，寻找髋臼内壁截骨的合适内移范围。 方法：利用SolidWorks 2008软件建立髋臼发育不良骨盆的三维模型，模拟髋臼内壁内移截骨术式，使髋臼内壁骨从未完全陷入盆腔内保持2 mm骨性接触处开始，逐渐内移至完全陷入盆腔内7 mm处，每隔1 mm为1个实验组，分成10个实验组。将每组髋臼人为划成4个象限，分别对各组假体髋臼-骨界面间进行计算机模拟对比力学实验分析，测量出髋臼假体-骨界面间的Mises应力及剪切应力值。 结果与结论：第1，5，6，9，10组在后下、前上、前下3个象限内的Mises应力分布不均匀；第2，3，4，7，8 组在后下、前上、前下3个象限内的Mises应力分布均匀，其中第4组Mises应力分布更为均匀。第2，3，4，7，8组在上述3个象限内的剪切应力分布均匀，第7，8组剪切应力最小。提示关节力在髋臼内的分布主要集中在后上象限，随着臼杯不断内移，臼杯与骨的接触面积会逐渐增大，从而增加接触面上的Mises应力，但剪切应力随髋臼内壁的内移而减小。因此髋臼内壁截骨合适的内移范围在未入盆腔内1 mm到完全陷入盆腔1 mm，最佳位置在完全陷入盆腔1 mm处。

Finite element analysis of acetabular medial wall displacement osteotomy in adult acetabular dysplasia

BACKGROUND: Adult acetabular dysplasia in advanced stage combined with hip joint osteoarthritis should undergo total hip replacement. The severity of acetabular lesion is various in different patients, which leads to significantly increased difficulty in reestablishing acetabulum. Acetabular medial wall displacement osteotomy can solve the component of acetabular prosthesis, but the displacement range of the acetabular medial wall following osteotomy is controversial. OBJECTIVE: To look for a suitable displacement range of acetabular medial wall following osteotomy by computer-aided design finite element analysis. METHODS: SolidWorks 2008 software was used to establish three-dimensional models of acetabular dysplasia pelvis. Acetabular medial wall displacement osteotomy was simulated to make acetabular medial wall bone displace from 2 mm bone contact to 7 mm bone contact in the pelvic cavity. One experimental group was set at 1 mm intervals, totally 10 experimental groups. The acetabulum in each group was split into four quadrants. The prosthesis acetabulum-bone interface in each group was analyzed by computer simulation contrast mechanics experiment. The Mises stress and shear stress values were measured between acetabular prosthesis and bone interface. RESULTS AND CONCLUSION: In groups 1, 5, 6, 9 and 10, the Mises stress was unevenly distributed in posterior inferior, anterior superior and anterior inferior quadrants. In groups 2, 3, 4, 7 and 8, the Mises stress was evenly distributed in posterior inferior, anterior superior and anterior inferior quadrants. Of them, the stress was most even in the group 4. In groups 2, 3, 4, 7 and 8, the shear stress was evenly distributed in the above-mentioned three quadrants. The shear stress was lowest in the groups 7 and 8. These indicate that joint force in the acetabulum mainly focused in the posterior superior quadrant. With the displacement of acetabular cup, the contact area of acetabular cup and bone would gradually increase, which finally increased the Mises stress in the contact surface. However, shear stress decreased with displacement of acetabular medial wall. Therefore, the suitable displacement range of acetabular medial wall osteotomy is 1 mm away from the pelvic cavity and 1 mm complete embolism in the pelvic cavity. The optimal position was 1 mm complete embolism in the pelvic cavity.